The Longitudinal Optic Neuritis Study (LONS) is a five year follow up study of the more than 450 patients who will be entered into the NIH- funded Optic Neuritis Treatment Trial (ONTT). Optic neuritis is an inflammatory disease of the optic nerve which typically affects young adults. It is closely linked to multiple sclerosis. The major objectives of this study include (1) Assessment of the beneficial and adverse effects of the corticosteroid treatments prescribed in the ONTT (oral prednisone and intravenous methylprednisolone) for a longer period of time than the six month follow up period of the ONTT, (2) Determination of the natural history of vision in patients who suffer optic neuritis, (3) Identification of risk factors and development of a predictive model for the development of multiple sclerosis in patients with optic neuritis, and (4) Determination of the importance of a positive antinuclear antibody (ANA) test in patients with optic neuritis. Patients will be seen at the 15 participating clinics throughout the United States on a yearly basis for ocular and neurologic examinations and visual function testing. Formalized phone contacts occur during the year. An elaborate system to maintain a high rate of patient participation has been established. Special measures are in place to monitor adherence to the protocol in the children. This multi-center collaborative effort is coordinated by the University of South Florida which serves as the data repository and analysis center. This study will answer any very important questions about the course of vision in optic neuritis and the relationship between optic neuritis and multiple sclerosis.